Quantitative Index And Classification Method For Judging The Strength Of Thixotropy Of Structural Clay In Zhanjiang Formation

The strong thixotropy of Zhanjiang Formation strong structural clay has strong thixotropy,the existence of thixotropy has a great influence on the engineering practice,the engineering community is unable to properly consider the impact of the thixotropy of Zhanjiang Formation clay on the actual engineering,which limits the application of Zhanjiang Formation clay as foundation in engineering construction.In this paper,the influence of physical and mechanical properties of soil on thixotropy of Zhanjiang Formation structural clays with different sensitivities was studied by using water content,porosity ratio and clay content as factors to conduct unconfined orthogonal test of compressive strength.The degree of influence of various factors on thixotropy of structural clay in Zhanjiang Formation was analyzed by visual analysis method,and the order of importance of influence of various factors on thixotropy of structural clay in Zhanjiang Formation was analyzed by range and variance analysis method.Based on the fuzzy mathematics theory,according to the influence factors of clay thixotropy,build to clay content,moisture content,void ratio and sensitivity for the index system of clay thixotropic strength fuzzy comprehensive evaluation factor set,set up the clay thixotropy comment set and thixotropy of the comprehensive evaluation of intensity grade standard of the evaluation index of intensity,the fuzzy mathematics comprehensive evaluation method to calculate the membership degree and weight of each index,set up the classification standard of clay thixotropic strength,and use this standard in zhanjiang group structured clay thixotropic strength for grading.The main work and conclusions of this paper are as follows:(1)The structural clays of Zhanjiang Formation with high sensitivity,medium sensitivity and low sensitivity were selected for physical and mechanical properties tests,which provided a basis for the selection of thixotropy grading indexes and the design of orthogonal test scheme.(2)Selecting four indicators such as clay content,moisture content,void ratio,sensitivity and so on,as the main factors influencing the structural clay thixotropy of zhanjiang group,and respectively to the high,medium and low sensitivity of structural clay in zhanjiang group unconfined compressive strength of orthogonal test,according to the result of orthogonal experiment,through the intuitive analysis and extreme difference analysis and variance analysis,the clay content,moisture content,void ratio,the sensitivity of structural clay in zhanjiang group thixotropic strength and thixotropic strength ratio and the influence of primary and secondary order.The results show that the thixotropic strength of structural clay in Zhanjiang Formation decreases with the increase of clay content,water content and pore ratio,and is negatively correlated with clay content,water content and pore ratio,while increases with the increase of sensitivity,and is positively correlated with the sensitivity.The thixotropic strength ratio increases with the increase of clay content,water content and sensitivity,and is positively correlated with clay content,water content and porosity ratio,but decreases with the increase of porosity ratio,and is negatively correlated with porosity ratio.For the same sensitive soil,the order of the influence of other factors on thixotropy is that the porosity ratio is greater than the moisture content and the moisture content is greater than the clay content.(3)Based on the classification method of fuzzy mathematics theory,according to the results of unconfined compressive strength orthogonal test and the classification standard of engineering soil,considering the importance of the influencing factors of clay thixotropy,the evaluation set of comprehensive evaluation of clay thixotropy strength and the grading standard of thixotropy strength evaluation index were established.The weight of each index was determined by the sum product method,the membership function of each index was determined by the trapezoidal distribution function,the membership degree of each index was calculated according to the membership function,and the thixotropy strength grading method of Zhanjiang Formation clay was obtained by combining the index weight and the single factor evaluation matrix determined by the membership degree.Use a group of zhanjiang clay thixotropic strength grading methods,the ray north river facies,estuarine facies,neritic facies and reenen of fluvial facies in zhanjiang group of thixotropic strength strong structural clay were classified,the results show that the strong thixotropy of the strong structural clay of Zhanjiang Formation is strong in different sedimentary facies,and the order of thixotropy is as follows: the Lenan fluvial facies is greater than the shallow Marine facies,the shallow Marine facies is greater than the estuarine facies,the estuarine facies is greater than the Leibei fluvial facies.